Well, the question could be reframed as 'when does the falling of hair be of concern?' This is because, medically, some amount of hair falling has been considered 'normal'. Hair being an appendage of the body like nails, they grow and fall constantly, in varying degree.
Medically speaking, for an adult, about 40 to 80 hair falling a day is considered within a normal range. It simply means that one may not consider getting treated for it if this is the case. However, it is also important that if one observes sudden increase of hair falling even within the normal range, it calls for medical attention and evaluation. Again, if one has hair falling within normal range but if they fall from the roots amounting to a definite reduction in the quantum of the total hair on the scalp, it calls for appropriate treatment. In any case, consistent hair falling over 80 a day and/or reduced hair quantum needs to be evaluated for treatment. Localized hair falling, leading to even a tiny hairless spot (alopecia) should always be studied and treated.
In this phase, the hair grows rapidly from the follicle. This phase usually lasts for about 1000 days; however, it may range form 2 to 6 years. Longer the anagen phase, the longer the hair will grow.
This is a regressive phase lasting for about 2 weeks. In this phase, the hair stops growing, the follicle shrinks and part of it may die.
This is the final resting end phase of hair growth cycle; no further change occurs now. This phase may last for about 2 to 4 months.
Later on, the hair follicle becomes active again developing new hair and forcing old Telogen hair out. At any given time, 90% of hair is in Anagen phase and 10% in Telogen phase. A reversal of the ratio results in thinning of hair.
There may be one or multiple factors leading to hair loss, which may be summarized as under:
Nutritional deficiency (Iron, Protein, zinc, etc.)
Local factors (Skin diseases like Psoriasis, Lichen Planus, etc.)
Hormonal factors (Hyper or hypothyroid, menopause)
Systemic disease (Liver disease, kidney failure)
After acute ailments (Viral infection, Typhod)
Stress factors (Anxiety, depression)
Drugs (Betablockers for hypertension, chemotherapy, anticholesterol drugs, etc.)
Male pattern baldness tends to be genetic in nature and is associated with high levels of circulating testosterone hormone which gets converted to dehydrotestosterone(DHT) which binds the root of the hair follicle, triggering hair loss.
Some of the local factors or conditions associated with hair loss are:
Local skin disorders:
Certain local skin ailments are known to lead to hair falling. Local skin infections such as Fungal infection (Tinea capitis), pyoderma, secondary syphilis, etc. Non-infectious conditions such as Dandruff, psoriasis, lichen planus, eczema, etc.
Local exposure to toxins:
Over use or abuse with chemical based shampoos, soaps, lotions are known to produce hair falling.
Unhygienic measures in scalp care may lead to hair falling. For instance, infrequent head wash, over exposure to harsh sun without protection, exposing the head to industrial fumes, etc.
Overall all deficiency of nutrition may affect the growth and quality of hair. Deficiency of vitamins B Group, Vitamin A, may lead to hair falling. Deficiency in proteins, iron, certain minerals may affect the hair growth, leading to hair falling. Iron deficiency due to a wide range of reasons such as excessive bleeding, restricted intake of iron forms an important cause of hair falling, especially found in females. The deficiency as above may be either due to faulty intake or which may have occurred due to certain systemic disorders such as Mal-assimilation or mal-absorption syndrome. It may occur following any prolonged acute or sub-acute diseases such as Irritable Bowel syndrome.
Certain hormones including androgen, estrogen and progesterone variations during different phases in life may bring about hair falling in excess. Thyroid hormones form another important group of disorders responsible for hair falling in some cases. Menopausal age hence makes one prone to have hair falling. Post pregnancy and child-birth is another example.
Certain acute diseases are known to leave behind a weakened vitality leading one to have hair falling. For examples: Pneumonia, viral infections, typhoid, etc.
Medicine and Drug induced:
Certain chemical medicines have known toxicity on the hair roots and growth. Long term use of chemotherapy, cancer medication, steroids, antibiotics, antiepileptic, antihypertensive medications etc. have been observed to produce hair falling in some patients, as per a study at our center. Contraceptive tablets are also known to induce hair falling.
The mind plays a vital role in maintaining the health in general developing a wide range of disorders, such as hair falling in particular.
Emotional stress is an epidemic condition prevailing in the world today. There is no single emotion, which may be figured out as a victim. In our experience, any and every emotion, which was experienced intensely, may cause a constitutional disorder affecting the physiological functioning of the hair growth.
Some of the examples of emotional stress may be summarized in brief as under: Intense anxiety about any important matter. Sadness or depression in one's life, which may be arising after marital disharmony or job dissatisfaction or unhappy social structure, etc. Grief due to unexpected events in one's life such as loss of a family member, loss in business, major set back in life, etc. A long-standing fear and apprehensive habit. And so on. Similarly, certain unhealthy attitudes such as aggressive behavior, violent expressions, hurried and impatient behavior, and like.